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 Department: Department of Chemistry
 Collection: UNT Theses and Dissertations
Computational Study of Small Molecule Activation via Low-Coordinate Late First-Row Transition Metal Complexes

Computational Study of Small Molecule Activation via Low-Coordinate Late First-Row Transition Metal Complexes

Date: May 2010
Creator: Pierpont, Aaron
Description: Methane and dinitrogen are abundant precursors to numerous valuable chemicals such as methanol and ammonia, respectively. However, given the robustness of these substrates, catalytically circumventing the high temperatures and pressures required for such transformations has been a challenging task for chemists. In this work, computational studies of various transition metal catalysts for methane C-H activation and N2 activation have been carried out. For methane C-H activation, catalysts of the form LnM=E are studied, where Ln is the supporting ligand (dihydrophosphinoethane or β-diketiminate), E the activating ligand (O, NCH3, NCF3) at which C-H activation takes place, and M the late transition metal (Fe,Co,Ni,Cu). A hydrogen atom abstraction (HAA) / radical rebound (RR) mechanism is assumed for methane functionalization (CH4 à CH3EH). Since the best energetics are found for (β-diket)Ni=O and (β-diket)Cu=O catalysts, with or without CF3 substituents around the supporting ligand periphery, complete methane-to-methanol cycles were studied for such systems, for which N2O was used as oxygen atom transfer (OAT) reagent. Both monometallic and bimetallic OAT pathways are addressed. Monometallic Fe-N2 complexes of various supporting ligands (LnFe-N2) are studied at the beginning of the N2 activation chapter, where the effect of ligand on N2 activation in end-on vs. side-on N2 isomers ...
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FTIR-ATR Characterization of Hydrogel, Polymer Films, Protein Immobilization and Benzotriazole Adsorption on Copper Surface

FTIR-ATR Characterization of Hydrogel, Polymer Films, Protein Immobilization and Benzotriazole Adsorption on Copper Surface

Date: December 2007
Creator: Pillai, Karthikeyan
Description: Plasma polymerization techniques were used to synthesize and deposit hydrogel on silicon (Si) substrate. Hydrogel is a network of polymer chains that are water-insoluble and has a high degree of flexibility. The various fields of applications of hydrogel include drug release, biosensors and tissue engineering etc. Hydrogel synthesized from different monomers possess a common property of moisture absorption. In this work two monomers were used namely 1-amino-2-propanol (1A2P) and 2(ethylamino)ethanol (2EAE) to produce polymer films deposited on Si ATR crystal. Their moisture uptake property was tested using FTIR-ATR technique. This was evident by the decrease in -OH band in increasing N2 purging time of the films. Secondly, two monomer compounds namely vinyl acetic acid and glycidyl methacrylate which have both amine and carboxylic groups are used as solid surface for the immobilization of bovine serum albumin (BSA). Pulsed plasma polymerization was used to polymerize these monomers with different duty cycles. Initial works in this field were all about protein surface adsorption. But more recently, the emphasis is on covalent bonding of protein on to the surface. This immobilization of protein on solid surface has a lot of applications in the field of biochemical studies. The polymerization of vinyl acetic acid ...
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Synthesis and X-ray Diffraction Structures of 2-(2-thienylidene)-4,5-bis-(diphenylphosphino)-4-cyclopenten-1,3-dione and fac-BrRe(CO)3[2-(2-thienylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione]

Synthesis and X-ray Diffraction Structures of 2-(2-thienylidene)-4,5-bis-(diphenylphosphino)-4-cyclopenten-1,3-dione and fac-BrRe(CO)3[2-(2-thienylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione]

Date: December 2005
Creator: Pingali, Aparna
Description: Treatment of 4,5 bis-(diphenylphosphino)-cyclopenten-1,3 dione with thiophene carboxyaldehyde in dichloromethane, in the presence of molecular sieves results in a new heterocyclic compound, 2-(2-thienylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (ligand), with a high yield. This product was characterized by using both IR and NMR spectroscopic techniques and the solid-state structure of the ligand was determined using X-ray crystallography. When the ligand was treated with the solvent stabilized intermediate of ReBr(CO)5 with THF, a monomeric metal complex, fac-BrRe(CO)3[2-(2-thienylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione] was the result. The solid-state structure of the monomeric metal complex was determined using X-ray crystallography. Photolysis and thermolysis studies of the complex will be further explored.
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Investigation of Structure and Properties of Low Temperature Deposited Diamond-Like Carbon Films

Investigation of Structure and Properties of Low Temperature Deposited Diamond-Like Carbon Films

Date: August 2004
Creator: Pingsuthiwong, Charoendee
Description: Electrodeposition is a novel method for fabrication of diamond-like carbon (DLC) films on metal substrates. In this work, DLC was electrochemically deposited on different substrates based on an anodic oxidation cyclization of acetylene in liquid ammonia. Successfully anodic deposition was carried out for DLC onto nickel substrate at temperatures below -40°C. Comparative studies were performed on a series of different carbon sources (acetylene, sodium acetylide, and a mixture of acetylene and sodium acetylide). The films were characterized using a variety of methods including Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), XPS valence band spectra, and/or scanning electron microscopy (SEM). Raman spectroscopy is used as a bench mark technique to verify the presence of deposited DLC films, to access the films homogeneities, and to provide the ratio of the different carbon phases, mainly disordered graphite (D) and graphite (G) phases in the films. A combination of the Raman with FTIR and valence band spectra analysis allowed the distinction between hydrogenated DLC and unhydrogenated DLC films. Three different kinds of DLC [(1) hydrogenated DLC (a-C:H); (2) tetrahedral hydrogenated DLC (ta-C:H); and (3) graphitic-like DLC] were deposited depending upon the deposition conditions and substrates. Temperature and current density are ...
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Investigation of the Possible Application of High and Low Frequency Conductance Measurements to the Analysis of Poly-Component Systems

Investigation of the Possible Application of High and Low Frequency Conductance Measurements to the Analysis of Poly-Component Systems

Date: 1956
Creator: Pinkerton, K. Allan
Description: The immediate goal of this thesis was the analysis of a three-component system whose major component was water. This analysis was to be the result of a procedure which could be readily extended to more complex systems.
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The Exchange of Bismuth Tetra-Iodide and Bismuth Ions in an Ion-Precipitate System

The Exchange of Bismuth Tetra-Iodide and Bismuth Ions in an Ion-Precipitate System

Date: 1952
Creator: Pitts, James William
Description: This paper is a study of the exchange of bismuth tetra-iodide and bismuth ions in an ion-precipitate system.
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Pyridine Derivatives of Naphthoquinone

Pyridine Derivatives of Naphthoquinone

Date: August 1954
Creator: Platas, Oscar R.
Description: This paper deals with the preparation of pyridinium derivatives of naphthoquinone. The starting material was 2,3-dichloro-1,4-naphthoquinone, and it was reacted with pyridine and 4-n-alkyl-pyridine derivatives.
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Hydrogen terminated silicon surfaces: Development of sensors to detect metallic contaminants and stability studies under different environments

Hydrogen terminated silicon surfaces: Development of sensors to detect metallic contaminants and stability studies under different environments

Date: August 2002
Creator: Ponnuswamy, Thomas Anand
Description: Hydrogen terminated silicon surfaces have been utilized to develop sensors for semiconductor and environmental applications. The interaction of these surfaces with different environments has also been studied in detail. The sensor assembly relevant to the semiconductor industry utilizes a silicon-based sensor to detect trace levels of metallic contaminants in hydrofluoric acid. The sensor performance with respect to two non-contaminating reference electrode systems was evaluated. In the first case, conductive diamond was used as a reference electrode. In the second case, a dual silicon electrode system was used with one of the silicon-based electrodes protected with an anion permeable membrane behaving as the quasi reference electrode. Though both systems could function well as a suitable reference system, the dual silicon electrode design showed greater compatibility for the on-line detection of metallic impurities in HF etching baths. The silicon-based sensor assembly was able to detect parts- per-trillion to parts-per-billion levels of metal ion impurities in HF. The sensor assembly developed for the environmental application makes use of a novel method for the detection of Ni2+using attenuated total reflection (ATR) technique. The nickel infrared sensor was prepared on a silicon ATR crystal uniformly coated by a 1.5 micron Nafion film embedded with dimethylglyoxime ...
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Synthesis and characterization of quinoxaline-functionalized, cage-annulated oxa- and thiacrown ethers and reaction chemistry of the diphosphine ligand 2,3-bis(diphenylphosphino)-N-p-tolylmaleimide (bmi) at triosmium carbonyl clusters.

Synthesis and characterization of quinoxaline-functionalized, cage-annulated oxa- and thiacrown ethers and reaction chemistry of the diphosphine ligand 2,3-bis(diphenylphosphino)-N-p-tolylmaleimide (bmi) at triosmium carbonyl clusters.

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Date: December 2006
Creator: Poola, Bhaskar
Description: Quinoxaline-functionalized, cage-annulated oxa- and thiacrown ethers have been synthesized as possible specific metal host systems. The synthesis and characterization of quinoxaline-functionalized, cage-annulated oxa- and thiacrown ethers have been described. The characterization of these host systems have been fully achieved in solution by using various techniques such as IR, 1H NMR, and 13C NMR spectroscopic methods, high-resolution mass spectrometry (HRMS), elemental microanalysis, and X-ray crystallographic analysis in case of one quinoxaline-functionalized, cage-annulated oxacrown ether compound. The synthesis of the diphosphine ligand 2,3-bis(diphenylphosphino)-N-p-tolylmaleimide (bmi) is described. The substitution of the MeCN ligands in the activated cluster 1,2-Os3(CO)10(MeCN)2 by the diphosphine ligand bmi proceeds rapidly at room temperature to furnish a mixture of bridging and chelating Os3(CO)10(bmi) isomers and the ortho-metalated product HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)N(tolyl-p)C(O)]. Thermolysis of the bridging isomer 1,2-Os3(CO)10(bmi) under mild conditions gives the chelating isomer 1,1-Os3(CO)10(bmi), whose molecular structure has been determined by X-ray crystallography. The kinetics for the ligand isomerization have been investigated by UV-vis and 1H NMR spectroscopy in toluene solution over the temperature range of 318-348 K. On the basis of kinetic data conducted in the presence of added CO and the Eyring activation parameters, a non-dissociative phosphine migration across one of the Os-Os bonds is proposed. Orthometalation of ...
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Podcast Effectiveness as Scaffolding Support for Students Enrolled in First-Semester General Chemistry Laboratories

Podcast Effectiveness as Scaffolding Support for Students Enrolled in First-Semester General Chemistry Laboratories

Date: August 2010
Creator: Powell, Mary Cynthia Barton
Description: Podcasts covering essential first-semester general chemistry laboratory techniques and central concepts that aid in experimental design or data processing were prepared and made available for students to access on an as-needed basis on iPhones- or iPod touches-. Research focused in three areas: the extent of podcast usage, the numbers and types of interactions between instructors and research teams, and student performance on graded assignments. Data analysis indicates that the podcast treatment research teams accessed a podcast 2.86 times on average during each week that podcasts were available. Comparison of interaction data for the lecture treatment research teams and podcast treatment research teams reveals that interactions with instructors were statistically significantly fewer for teams that had podcast access rather than a pre‐laboratory lecture. The implication of the results is that student research teams were able to gather laboratory information more effectively when it was presented in an on-demand podcast format. Finally, statistical analysis of data on student performance on graded assignments indicates no significant differences between outcome measures for the treatment groups when compared as cohorts. The only statistically significant difference is between students judged to be highly motivated; for this sub‐group the students in the podcast treatment group earned a ...
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